北极楚克奇陆架边缘“大西洋水层”钕同位素示踪  

Arctic Neodymium Isotope Traces for the Atlantic Water Layer at the Chukchi Continental Margin

作　　者：杨映 叶黎明 倪建宇 于晓果 原超 葛倩 宋赛 张泳聪 Yang Ying;Ye Liming;Ni Jianyu;Yu Xiaoguo;Yuan Chao;Ge Qian;Song Sai;Zhang Yongcong(Key Laboratory of Submarine Geosciences&Second Institute of Oceanography,Ministry of Natural Resources,Hangzhou 310012,China;School of Geography and Ocean Science,Nanjing University,Nanjing 210023,China)

机构地区：[1]自然资源部海底科学重点实验室&自然资源部第二海洋研究所,浙江杭州310012 [2]南京大学地理与海洋科学学院,江苏南京210023

出　　处：《地球科学》2024年第8期2938-2951,共14页Earth Science

基　　金：自然资源部第二海洋研究所中央级公益性科研院所基本科研业务费专项资金(No.JG1512)。

摘　　要：温暖的“大西洋水层”为北冰洋提供了重要的热量来源,是决定其海冰状况、冰架分布及周边冰盖稳定性的关键因素.通过分析M04孔沉积物中稀土元素(REE)的含量及其配分模式和Fe-Mn氧化物组分的钕同位素组成,探讨了晚更新世以来楚克奇陆架边缘REE的富集机制、εNd示踪水团性质的有效性以及“大西洋水层”的强弱变化.结果表明,间冰期Fe-Mn氧化物是溶解态REE沉淀的主要载体,但冰期缺少Fe-Mn氧化物的灰色层中也富集了大量的溶解态REE.同时,Fe-Mn氧化物萃取液中εNd介于—5.50~—8.74之间,呈现出冰期高,间冰期低的特点,有效指示了“大西洋水层”在楚克奇陆架边缘的活动.在间冰期,“大西洋水层”增强,为陆架输入的Fe2+和Mn2+创造了再氧化的条件;而在冰期,“大西洋水层”几乎退出了楚克奇陆架边缘.参照现代冰川溶水的化学组成,导致冰期M04孔Fe-Mn氧化物萃取液中REE富集和εNd显著正偏的环境要素,很可能是东西伯利亚冰盖的扩张及其冰下排水,而不是海冰排盐形成的“卤水”.这些发现进一步揭示了北冰洋REE的富集机制,论证了εNd示踪“大西洋水层”的有效性,并深化了对“大西洋水层”演变规律的认知.In the Arctic Ocean,the Atlantic water layer is an essential source of heat that regulates sea ice,ice shelves,and surrounding ice sheets.By analyzing the content and pattern of rare earth elements(REE)and Nd isotopic composition(εNd)in the sediments of Hole M04 and its distribution pattern and Nd isotopic composition of Fe-Mn oxide fraction,this study explores the enrichment mechanism of REE on the edge of Chukchi shelf since Late Pleistocene,the effectiveness ofεNd tracer water mass properties,and the strength and weakness of the"Atlantic water layer".The records indicate that Fe-Mn oxides were the primary carriers for dissolved REE during the interglacial period,but a large quantity of dissolved REE was also enriched in the gray layer lacking Fe-Mn oxides.In addition,there is a significant spike ofεNd in Fe-Mn oxide leachate during the glacial period and a drop during the interglacial period corresponding to values between −5.50 and −8.74. Therefore, we conclude that the Atlantic water layer strengthened during the interglacial period, which allowed re-oxidation of Fe2+ and Mn2+ input from the shelf, but withdrew almost entirely from the Chukchi continental margin during the glacial period. Similar to the chemical composition of modern glacial meltwater, the development of the East Siberian ice sheet and its subglacial drainage are more likely to lead to the REE enrichment and εNd positive bias in Core M04 Fe-Mn oxide extraction solution than sea ice production brine. These findings further illustrate the process of enrichment of REEs in the Arctic Ocean, demonstrate the effectiveness of εNd as a marker of the Atlantic water layer, and contribute to an understanding of the Atlantic water layer evolution.

关 键 词：钕同位素 稀土元素 大西洋水层 楚克奇陆架边缘 北冰洋 海洋地质 

分 类 号：P736[天文地球—海洋地质]